Location: Livestock Bio-Systems
2024 Annual Report
Objectives
Objective 1. Improve postnatal survival of preweaning piglets by identifying factors that contribute to within-litter variations on piglet growth and development.
Sub-objective 1.A: Determine the influence of ovarian responses (OR and serum P4 levels) during early gestation on within-litter variation in embryo elongation and uterine environmental responses in young females (Exp. 1) and multi-parous sows (Exp. 2).
Sub-objective 1.B: Evaluate the influence of regulatory factors (i.e., miRNAs) and nutrient transfer (i.e., metabolites) from maternal to fetal plasma across the placenta on divergent-sized fetal growth and within-litter variation during late gestation using a global approach (i.e., RNA-seq and non-targeted metabolomics, respectively).
Objective 2. Discover nutritional and environmental influences on gilt development and productivity to minimize reproductive failure of replacement gilts.
Sub-objective 2.A: Improve gilt development by understanding how growth relates to prebreeding anestrus.
Sub-objective 2.B: Minimize pubertal failure in gilts by identifying mechanisms in the anterior pituitary gland that are mediating the effects of nutrient balance on secretion of gonadotropin hormones necessary for initiation and maintenance of reproductive cycles.
Sub-objective 2.C: Improve neonatal management of replacement gilts by identifying how colostrum intake impacts early ovarian development.
Objective 3. Identify and evaluate biological predictors of sow performance and longevity within the breeding herd.
Sub-objective 3.A: Identify plasma biomarkers and blood transcript profiles from young pre-breeding females and associate those profiles with their subsequent breeding herd longevity.
Sub-objective 3.B: Evaluate USMARC swine population for effects of seasonal climate upon production parameters over the past decade.
Sub-objective 3.C: Generate hypomethylated, hypermethylated, or control pregnancies during summer or winter months to determine epigenetic impact upon placental, fetal, and piglet production.
Objective 4. Utilize and develop precision management technologies to improve preweaning piglet survival, gilt development, and sow longevity and increase efficiency of pork production.
Sub-objective 4.A.: Utilize ESF data to develop prediction models for gilt fertility (e.g., behavioral estrus) and sow welfare during gestation (e.g., abortion/miscarriage, lameness, appropriate body weight).
Approach
Pork is the most consumed meat animal product globally. Improving lifetime efficiency of swine is critical to support an increasing global population. Improved lifetime efficiency will provide a high-quality source of protein while reducing the impact of swine production on the environment and ensuring the social welfare of animals. Lifetime efficiency is a complex trait that is influenced by genetic, environment, and management components. The comprehensive goal for this project is to further our understanding of these traits using physiology-, biology-, and technology-based approaches to provide improvements for fetal and neonatal health, gilt development, and sow longevity. We will accomplish this goal utilizing independently, and in combination, transcriptomics, metabolomics, proteomics, environmental data, and automated precision measurements (Figure 1). Within objective 1, we will investigate molecular pathways and signals that improve production of consistently sized piglets initiated shortly after conception. Objective 2 will delve into the influence nutrition has on the young female and the impact upon neuroendocrine gene expression as the gilt transitions into the active state of reproduction. Identifying biological markers that can assist in selecting females with longevity in the breeding system and investigating climate and therapeutics to assist with stayability are the central themes of Objective 3. In the fourth objective, feeding behavior and activity measurements of young gilts and gestating females will be collated and activity patterns will be generated to predict reproductive success or failure. The projects designed herein will clarify and contribute to the existing complex knowledge gap of swine productive life. Application of these studies will result in breeding females that are consistently well adapted, produce large litters of uniform piglets and remain fertile and healthy in the swine herd increasing production efficiency, improve economic competitiveness of U.S. pork producers, and contribute to basic understanding of biological and environmental influences upon swine production.
Progress Report
Progress has been made to address the four objectives for the project, Improving Lifetime Productivity in Swine using Systems Biology and Precision Management over the past year. Within Objective 1, a large-scale, retrospective evaluation of uterine capacity during late gestation in young (gilts) commercial females over the past twenty years has demonstrated recent increases in the uterine capacity have been driven, in part, by indirect selection of increased ovulation rates in commercial line pigs. While increased uterine capacity does not appear to negatively impact fetal growth in gilts, there are some negative impacts on placental growth and development. Therefore, using approaches to target improved placental development and function provides a potential mechanism to improve piglet litter quality and weaning survivability. We are augmenting some of our research in Objective 1 towards evaluating feed additives in gestation diets specifically formulated to target placental vascular and structural development. In support of Objective 2, we continue research to collect data on pubertal phenotypes and add data from electronic sow feeder (ESF) in breeding. An additional 750-1500 records were added to the database that contain ESF body weight data and pubertal phenotypes during boar stimulation. The amount of data generated has been less than anticipated due to management of porcine reproductive and respiratory syndrome virus (PRRSV) outbreak.
We continue to research biological mechanisms within the anterior pituitary gland responsible for nutritional mediated secretion of gonadotropin hormones and acyclicity within Objective 2. Sequencing of RNA from gilts in different states of nutrition have been completed using a novel pooling strategy. These differences in gene transcripts will be correlated with changes in pituitary proteome. We have completed laboratory analysis and received raw proteomic data. Currently we are processing these data for analysis. Gene expression has been compared between cyclic and acyclic gilts across multiple tissues that regulate reproduction. This is the most comprehensive study of the subject in any mammalian species that reveals novel mechanisms within the anterior pituitary gland that involved components of the immune system and thyroid stimulation that are important for activation of gonadotropin secretion to support ovarian function and cyclicity in gilts. These data have further established that failure to reach puberty at normal breeding ages are associated with key genes in the hypothalamus that activate gonadotrope cells in the anterior pituitary gland for secretion of hormones that activate ovarian development.
In support of Objective 3, efforts are underway to create a large dataset coordinating environmental data (temperature, humidity, and light), dam feeding activity and body weights from electronic sow feeders, and farrowing performance records. Our interest lies in better understanding subtle alterations via physical environment or behavior (feeding activity) and the subsequent impact upon farrowing activity. Ultra-performance liquid chromatography - tandem mass spectrometry (UPLC-MSMS) abundance data from young gilts (approximately 140 days of age) that remained in the breeding herd through four parities will be analyzed, Summer 2024, to determine early life biomarkers that may assist in predicting females that will farrow and wean either small litters or large litters in their lifetime. Finally, a project to generate hypo-and hyper-methylated placenta in summer and winter has been initiated and will begin early August to determine if altering methylation state during early pregnancy in the gilt will improve farrowing rates and performance during seasonal periods.
Within Objective 4, progress continues with the collection of electronic data from sow feeders in the gilt development and gestation barns capturing feeding activity/behavior and body weights stored onto the relational database. Physiological events such as estrus activity, health and welfare, farrowing traits, and culling/removal events are being collected by trained animal caretakers and stored on the relational database.
All scientists within the project are actively engaged in participation with externally funded proposals (over $1.5 million) that compliment efforts of our project plan, specifically aspects of lifetime productivity of swine. In support of Objective 1 and with academic partners, a funded proposal investigating components associated with extracellular vesicles in early pregnancy of the pig and how those compounds contribute to development and survival of pig embryos continues. Another collaborative externally funded project investigates thermal heat stress on boar fertility and how this can indirectly impact successful pregnancy rates supports Objective 2. A third externally funded project, in collaboration with academic colleagues, will investigate the use of essential oils in lieu of antibiotic use and the reproductive performance of sows following weaning in support of Objective 3, sow lifetime productivity. A continued collaborative multi-state institution project that supports precision management efforts by investigating the uses of sensors that measure the vibrational movement of flooring and animal pen features to monitor sow and piglet activity lends itself to the work being done in Objectives 1 and 4. A newly established research agreement has been initiated in which ARS scientists are using novel feed additives in swine gestational diets to modify vascular and structural development of the placenta. This project supports efforts in Objectives 1 and 3 by investigating methods to improve prenatal survival and sow performance as measured by piglet production.
Accomplishments
1. Sensors monitor farrowing activity and piglet care by the mother sow. A huge challenge for today’s swine farms is providing 24-hour care by skilled laborers in the farrowing facility. Accurately identifying the time of farrowing or piglet distress would enable swine farms to provide fast directed care at critical timepoints without unnecessary disruptions to resting animals while minimizing labor demands. ARS researchers at Clay Center, Nebraska, along with collaborators from several U.S. academic institutions used seismic sensors to measure structure vibrations coming from both the sow and her piglets then applied predictive modeling to determine, with favorable accuracy, specific activities of sows before and during farrowing (birth/labor). Piglet activities (e.g., sleeping, suckling, playing, and distress) were also identified, and some of these traits predicted piglet growth. These results provide new ways to apply precision animal management for targeted animal care to enhance animal well-being and improve economic sustainability for swine producers.
2. Ideal birth weight and growth rate of gilts for reproductive selection. One of the greatest costs to swine production is that nearly 50% of breeding gilts are removed annually because they fail to produce a litter of piglets. Gilts can fail to become pregnant because they do not reach puberty (sexually immature) or fail to show signs of sexual receptivity (silent ovulation). Growth rate before breeding is thought to affect these conditions. ARS scientists at Clay Center, Nebraska, compared how body weight and growth rate affect puberty and silent ovulation in gilts. Sexually immature gilts weighed more at birth and gilts with silent ovulation grew faster than their littermates. These results indicate that swine producers should avoid selecting gilts with the smallest or largest birth weight as replacements and optimize, rather than maximize, prepubertal growth rates.
3. Composition of sow milk influences piglet growth throughout the suckling period. Early piglet health and growth is reliant upon milk from the mother. Increasing the gain of a piglet by 0.45 kg at weaning is associated with fewer days on feed for finished pigs to market, increasing profitability for producers. Investigations by ARS researchers at Clay Center, Nebraska, found that nursing sows with the highest level of lactose, a sugar in milk, during early lactation produced heavier piglets throughout the nursing period. Sows with higher levels of milk fat midway through the nursing phase also had heavier piglets at weaning. This information will help identify mother sows that genetically produce better quality milk and will also be used to develop feed supplements that support the production of beneficial milk components to improve piglet growth and health and producer profitability.
4. The biology behind sexual development in pigs. Gilts that fail to reach puberty (sexual maturity) are removed from the breeding herd at a financial loss to the producer. Understanding the physiological reasons causing pubertal failure is important to reduce gilt removal thereby reducing costs for pork producers. ARS scientists at Clay Center, Nebraska, compared expression of genes in the tissues important for reproduction from sexually immature and mature gilts at similar ages. Researchers found critical genes with reduced expression in several tissues, such as the brain and the ovary of the immature gilts compared to mature gilts. These changes in gene expression can lead to insufficient production of reproductive hormones necessary for sexual development. These results will help producers to optimize reproductive development of gilts and reduce the culling rate of the breeding herd.
Review Publications
Wijesena, H.R., Keel, B.N., Nonneman, D.J., Cushman, R.A., Lents, C.A. 2023. Clustering of multi-tissue transcriptomes in gilts with normal cyclicity or delayed puberty reveals genes related to pubertal development. Biology of Reproduction. 110(2):261-274. https://doi.org/10.1093/biolre/ioad145.
Dong, Y., Bonde, A., Codling, J.R., Bannis, A., Cao, J., Macon, A., Rohrer, G., Miles, J., Sharma, S., Brown-Brandl, T., Sangpetch, A., Sangpetch, O., Zhang, P., Noh, H. 2023. PigSense: Structural vibration-based activity and health monitoring system for pigs. ACM Transactions on Sensor Networks. 20(1):1-43. https://doi.org/10.1145/3604806.
Wijesena, H.R., Nonneman, D.J., Rohrer, G.A., Lents, C.A. 2023. Relationships of genomic estimated breeding values for age at puberty, birth weight, and growth during development in normal cyclic and acyclic gilts. Journal of Animal Science. 101. Article skad258. https://doi.org/10.1093/jas/skad258.
Rempel, L.A., Oliver, W.T., Miles, J.R. 2023. Early- and mid-lactation milk traits are associated with piglet growth during lactation. Journal of Animal Science. 101. Article skad340. https://doi.org/10.1093/jas/skad340.
Harlow, K., Summers, K., Oliver, W.T., Wells, J., Ferguson, M., Crouse, M.S., Neville, B.W., Rempel, L.A., Rivera-Colon, I., Ramsay, T.G., Davies, C.L. 2024. Weaning transition, but not the administration of probiotic candidate Kazachstania slooffiae, shaped the gastrointestinal bacterial and fungal communities in nursery piglets. Frontiers in Veterinary Science. 10. Article e1303984. https://doi.org/10.3389/fvets.2023.1303984.
Cushman, R.A., Yake, H.K., Snider, A.P., Lents, C.A., Murphy, T.W., Freking, B.A. 2023. An extreme model of fertility in sheep demonstrates the basis of controversies surrounding antral follicle count and circulating concentrations of anti-Müllerian hormone as predictors of fertility in ruminants. Animal Reproduction Science. 259. Article 107364. https://doi.org/10.1016/j.anireprosci.2023.107364.
Cushman, R.A., Akbarinejad, V., Perry, G.A., Lents, C.A. 2024. Developmental programming of the ovarian reserve in livestock. Animal Reproduction Science. 264. Article 107458. https://doi.org/10.1016/j.anireprosci.2024.107458.